Searcharxiv⌕ Search

arXiv subjects

A. Sheykhi

Publications and source records attributed to A. Sheykhi.

At least 109 records · Page 6Linked to original sources

Thermodynamic instability of charged dilaton black holes in AdS spaces

We study thermodynamic instability of a class of $(n+1)$-dimensional charged dilaton black holes in the background of anti-de Sitter universe. We calculate the quasilocal mass of the AdS dilaton black hole through the use of the subtraction method of Brown and York. We find a Smarr-type formula and perform a stability analysis in the canonical ensemble and disclose the effect of the dilaton field on the thermal stability of the solutions. Our study shows that the solutions are thermally stable for small $α$, while for large $α$ the system has an unstable phase, where $α$ is a coupling constant between the dilaton and matter field.

hep-th↗

Interacting agegraphic quintessence dark energy in non-flat universe

We suggest a correspondence between interacting agegraphic dark energy models and the quintessence scalar field in a non-flat universe. We demonstrate that the agegraphic evolution of the universe can be described completely by a single quintessence scalar field. Then, we reconstruct the potential of the interacting agegraphic quintessence dark energy as well as the dynamics of the scalar field according to the evolution of the agegraphic dark energy.

hep-th↗

Charged rotating dilaton black branes in AdS universe

We present the metric for the $(n+1)$-dimensional charged rotating dilaton black branes with cylindrical or toroidal horizons in the background of anti-de Sitter spacetime. We find the suitable counterterm which removes the divergences of the action in the presence of the dilaton potential in all higher dimensions. We plot the Penrose diagrams of the spacetime and reveal that the spacetime geometry crucially modifies in the presence of the dilaton field. The conserved and thermodynamic quantities of the black branes are also computed.

hep-th↗

Magnetic Branes in Brans-Dicke-Maxwell Theory

We present a new class of magnetic brane solutions in $(n+1)$-dimensional Brans-Dicke-Maxwell theory in the presence of a quadratic potential for the scalar field. These solutions are neither asymptotically flat nor (anti)-de Sitter. Our strategy for constructing these solutions is applying a conformal transformation to the corresponding solutions in dilaton gravity. This class of solutions represents a spacetime with a longitudinal magnetic field generated by a static brane. They have no curvature singularity and no horizons but have a conic geometry with a deficit angle $δ$. We generalize this class of solutions to the case of spinning magnetic brane with all rotation parameters. We also use the counterterm method and calculate the conserved quantities of the solutions.

hep-th↗

Interacting agegraphic tachyon model of dark energy

Scalar-field dark energy models like tachyon are often regarded as an effective description of an underlying theory of dark energy. In this Letter, we implement the interacting agegraphic dark energy models with tachyon field. We demonstrate that the interacting agegraphic evolution of the universe can be described completely by a single tachyon scalar field. We thus reconstruct the potential as well as the dynamics of the tachyon field according to the evolutionary behavior of interacting agegraphic dark energy.

hep-th↗

Thermodynamics of Charged Brans-Dicke AdS Black Holes

It is well-known that in four dimensions, black hole solution of the Brans-Dikce-Maxwell equations is just the Reissner-Nordstrom solution with a constant scalar field. However, in $n\geq4$ dimensions, the solution is not yet the $(n+1)$-dimensional Reissner-Nordstrom solution and the scalar field is not a constant in general. In this paper, by applying a conformal transformation to the dilaton gravity theory, we derive a class of black hole solutions in $(n+1)$-dimensional $(n\geq 4)$ Brans-Dikce-Maxwell theory in the background of anti-de Sitter universe. We obtain the conserved and thermodynamic quantities through the use of the Euclidean action method. We find a Smarr-type formula and perform a stability analysis in the canonical ensemble. We find that the solution is thermally stable for small $α$, while for large $α$ the system has an unstable phase, where $α$ is a coupling constant between the scalar and matter field.

hep-th↗

Topological Black Holes in Brans-Dicke-Maxwell Theory

We derive a new analytic solution of $(n+1)$-dimensional Brans-Dikce-Maxwell theory in the presence of a potential for the scalar field, by applying a conformal transformation to the dilaton gravity theory. These solutions describe topological charged black holes with unusual asymptotics. We obtain the conserved and thermodynamic quantities through the use of the Euclidean action method. We also study the thermodynamics of the solutions and verify that the conserved and thermodynamic quantities of the solutions satisfy the first law of black hole thermodynamics.

hep-th↗

Higher Dimensional Charged Rotating Dilaton Black Holes

In this paper, we present the metric for the $n$-dimensional charged slowly rotating dilaton black hole with $N = [(n -1)/2]$ independent rotation parameters, associated with $N$ orthogonal planes of rotation in the background of asymptotically flat and asymptotically (anti)-de Sitter spacetime. The mass, angular momentum and the gyromagnetic ratio of such a black hole are determined for the arbitrary values of the dilaton coupling constant. We find that the gyromagnetic ratio crucially depends on the dilaton coupling constant, $α$, and decreases with increasing $α$ in any dimension.

hep-th↗

Higher dimensional slowly rotating dilaton black holes in AdS spacetime

In this paper, with an appropriate combination of three Liouville-type dilaton potentials, we obtain the higher dimensional charged slowly rotating dilaton black hole solution for asymptotically anti-de Sitter spacetime. The angular momentum and the gyromagnetic ratio of such a black hole are determined for the arbitrary values of the dilaton coupling constant. It is shown that the dilaton field modifies the gyromagnetic ratio of the rotating dilaton black holes.

gr-qc↗

Asymptotically flat charged rotating dilaton black holes in higher dimensions

We find a class of asymptotically flat slowly rotating charged black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling constant in higher dimensions. Our solution is the correct one generalizing the four-dimensional case of Horne and Horowitz \cite{Hor1}. In the absence of a dilaton field, our solution reduces to the higher dimensional slowly rotating Kerr-Newman black hole solution. The angular momentum and the gyromagnetic ratio of these rotating dilaton black holes are computed. It is shown that the dilaton field modifies the gyromagnetic ratio of the black holes.

hep-th↗

Magnetic Strings in Einstein-Born-Infeld-Dilaton Gravity

A class of spinning magnetic string in 4-dimensional Einstein-dilaton gravity with Liouville type potential which produces a longitudinal nonlinear electromagnetic field is presented. These solutions have no curvature singularity and no horizon, but have a conic geometry. In these spacetimes, when the rotation parameter does not vanish, there exists an electric field, and therefore the spinning string has a net electric charge which is proportional to the rotation parameter. Although the asymptotic behavior of these solutions are neither flat nor (A)dS, we calculate the conserved quantities of these solutions by using the counterterm method. We also generalize these four-dimensional solutions to the case of $(n+1)$-dimensional rotating solutions with $k\leq[n/2]$ rotation parameters, and calculate the conserved quantities and electric charge of them.

hep-th↗

Charged rotating black holes in dilaton gravity

We consider charged black holes with curved horizons, in five dimensional dilaton gravity in the presence of Liouville-type potential for the dilaton field. We show how, by solving a pair of coupled differential equations, infinitesimally small angular momentum can be added to these static solutions to obtain charged rotating dilaton black hole solutions. In the absence of dilaton field, the non-rotating version of the solution reduces to the five dimensional Reissner-Nordström black hole, and the rotating version reproduces the five dimensional Kerr-Newman modification thereof for small rotation parameter. We also compute the angular momentum and the angular velocity of these rotating black holes which appear at the first order.

hep-th↗

Magnetic Branes in $(n+1)$-dimensional Einstein-Maxwell-dilaton gravity

We construct two new classes of spacetimes generated by spinning and traveling magnetic sources in $(n+1)$-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type potential. These solutions are neither asymptotically flat nor (A)dS. The first class of solutions which yields a $(n+1)$-dimensional spacetime with a longitudinal magnetic field and $k$ rotation parameters have no curvature singularity and no horizons, but have a conic geometry. We show that when one or more of the rotation parameters are nonzero, the spinning branes has a net electric charge that is proportional to the magnitude of the rotation parameters. The second class of solutions yields a static spacetime with an angular magnetic field, and have no curvature singularity, no horizons, and no conical singularity. Although one may add linear momentum to the second class of solutions by a boost transformation, one does not obtain a new solution. We find that the net electric charge of these traveling branes with one or more nonzero boost parameters is proportional to the magnitude of the velocity of the branes. We also use the counterterm method and calculate the conserved quantities of the solutions.

hep-th↗

Thermodynamics of rotating black branes in $(n+1)$-dimensional Einstein-Born-Infeld-dilaton gravity

In this paper, we construct a new class of charged, rotating solutions of $% (n+1)$-dimensional Einstein-Born-Infeld-dilaton gravity with Liouville-type potentials and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We find that these solutions can represent black brane, with inner and outer event horizons, an extreme black brane or a naked singularity provided the parameters of the solutions are chosen suitably. We also compute temperature, entropy, charge, electric potential, mass and angular momentum of the black brane solutions, and show that these quantities satisfy the first law of thermodynamics. We find that the conserved quantities are independent of the Born-Infeld parameter $β$, while they depend on the dilaton coupling constant $α$. We also find the total mass of the black brane with infinite boundary as a function of the entropy, the angular momenta and the charge and perform a stability analysis by computing the heat capacity in the canonical ensemble. We find that the system is thermally stable for $α\leq 1$ independent of the values of the charge and Born-Infeld parameters, while for $α> 1$ the system has an unstable phase. In the latter case, the solutions are stable provided $α\leq α_{\max}$ and $β\geq β_{\min}$, where $% α_{\max}$ and $β_{\min}$ depend on the charge and the dimensionality of the spacetime. That is the solutions are unstable for highly nonlinear electromagnetic field or when the dilaton coupling constant is large.

hep-th↗

Boundary Conditions in Stepwise Sine-Gordon Equation and Multi-Soliton Solutions

We study the stepwise sine-Gordon equation, in which the system parameter is different for positive and negative values of the scalar field. By applying appropriate boundary conditions, we derive relations between the soliton velocities before and after collisions. We investigate the possibility of formation of heavy soliton pairs from light ones and vise versa. The concept of soliton gun is introduced for the first time; a light pair is produced moving with high velocity, after the annihilation of a bound, heavy pair. We also apply boundary conditions to static, periodic and quasi-periodic solutions.

hep-th↗

Thermodynamics of black holes in $(n+1)$-dimensional Einstein-Born-Infeld dilaton gravity

We construct a new class of $(n+1)$-dimensional $(n\geq3)$ black hole solutions in Einstein-Born-Infeld-dilaton gravity with Liouville-type potential for the dilaton field and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We find that these solutions can represent black holes, with inner and outer event horizons, an extreme black hole or a naked singularity provided the parameters of the solutions are chosen suitably. We compute the thermodynamic quantities of the black hole solutions and find that these quantities satisfy the first law of thermodynamics. We also perform stability analysis and investigate the effect of dilaton on the stability of the solutions.

hep-th↗

Asymptotically nonflat Einstein-Born-Infeld-dilaton black holes with Liouville-type potential

We construct some classes of electrically charged, static and spherically symmetric black hole solutions of the four-dimensional Einstein-Born-Infeld-dilaton gravity in the absence and presence of Liouville-type potential for the dilaton field and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We show that in the presence of the Liouville-type potential, there exist two classes of solutions. We also compute temperature, entropy, charge and mass of the black hole solutions, and find that these quantities satisfy the first law of thermodynamics. We find that in order to fully satisfy all the field equations consistently, there must be a relation between the electric charge and other parameters of the system..

hep-th↗